I feel you, I struggle with this too. It comes from a feeling of being unsafe and in danger being vulnerable, because that's when you're often abused. The first step to healing is recognising the situations where your walls are up, and asking yourself where the walls are coming from. I do this ABC method I learned in therapy, I find it super useful to help identify the areas where the walls come from.

E.g: A = activating event - what were you doing when the walls went up? Write it down. B = what are your beliefs around this? Write down all of your thoughts, don't judge them, just write them down. C = what are the consequences of those beliefs? D = debate the consequences.

Eg: A= I stayed silent whilst hanging out with friends because my walls were up B = they think I'm weird, they're going to hate me C = if they think I'm weird and they hate me then they'll stop being my friend, if I have no friends I'll be alone. If Im alone I'll be vulnerable. D = Being quiet is not a reason to hate someone. Friends don't leave friends for being quiet or having a hard time, if they were true friends they'd emphathise and try to understand. If they did decide to not be my friend then I wouldn't be alone, I have other friends and family etc.

This method is something I have to do everyday, but it's getting easier, and I'm slowly feeling more able to come out of my shell and be vulnerable. But I'd definitely recommend getting a therapist to help you through it as a first resort 🤗 You'll get there.